Viscous magnetization: misleading Koeningsberger's Q

Mineral explorationists who model and interpret magnetic data make the assumption that the vast majority of observed responses are due to induced magnetisation. Rock magnetists on the other hand have published tables showing that for most rocks the ratio of remanent to induced magnetisation (Koeningsberger Q) is much greater than unity, and that remanent magnetisation is the dominant source of magnetic anomalies ((Clark 1983)). This inconsistency between the two observations is difficult to resolve unless viscous magnetisation (VRM) is more important than has been previously recognised. VRM is a slowly acquired remanence that will lie in the direction of the local magnetic field and thus be parallel to the induced component. In order to correctly model and interpret the source of magnetic anomalies it is suggested that the VRM component needs to be routinely measured and considered. The measurement will however provide a considerable challenge. A revised parameter R consisting of the ratio of the TRM component to the (induced plus VRM components) is suggested to replace the Koeningsberger Q from a geophysical rather than a rock magnetic perspective.